What products in which context? Worldwide import or inland?
a) Buy to use?
b) Buy as parts to fabricate products?
c) Buy to sell?
d) Search to find new retail products in a certain cathegory?
Some different approaches could be used. Normally you will start searching 'normal way': use and interview known channels and users, market surveys etc, preliminary cost/benifit and cost/lifetiome analyzes. All this to have a detailed description of the framework around the products and the requirement for the products themselves.
Then first, do you start your search googling, additionally asking branch organizations, foreign trade or export organizations, friends and competitors, and generally enlarge your contact net.
Description and bidding processes?
Repeat until satisfactory result!